In known means of this kind the supply of lubricant to the metering pump is achieved by arranging that the metering pump is connected direct to the usual lubricant circuit which also feeds the bearings of the machine or engine with lubricant. Although this lubricant which is fed to the bearings is generally filtered it is not possible to avoid tiny worn particles or particles of dirt reaching the metering pump all the same and thereby adversely affecting the operation of the delicate components within the pump.